a. Field of the Invention
The present invention relates to a numerical control apparatus for controlling a multiple-axis and multiple-channel machine tool by controlling multiple axes through multiple channels, and more particularly, to a numerical control apparatus for controlling a multiple-axis and multiple-channel machine tool, provided with two buses and a plurality of servo command generating processors to enable data to be processed at a high speed.
b. Description of the Related Art
In a numerical control machine tool, a multitude of tool posts are provided so that a workpiece can be machined by a plurality of tools, to effect a higher speed machining of the workpiece.
FIG. 3 shows a schematic diagram of a numerical control lathe for use as a multiple-axis and multiple-channel machine tool having a plurality of tool posts, as an example of such a numerical control machine tool. In FIG. 3, numeral 61 denotes a main spindle, which is controlled in a Z-direction along a Z1-axis. In the numerical control lathe, the Z-axis is driven in synchronism with the rotation of the main spindle 61.
Numeral 62 denotes a first tool post, which is controlled only in an X-direction along an X1-axis. Namely, the main spindle 61 and the first tool post 62 constitute normal X-Z coordinates.
Numeral 63 denotes a second tool post, which is controlled in the X- and Z-directions along X2- and Z2-axes. When the main spindle 61 does not move along the Z1-axis, the second tool post 63 is driven at independent X-Z coordinates, but when the main spindle 61 does move in the Z1-axis direction, the movement of the second tool post 63 must take into account this movement in the Z1-axis direction, so that the movement of the Z2-axis is superposed on that of the Z1-axis. In other words, the Z2-axis must be moved for a distance equivalent to the sum of the original stroke of the Z2-axis and the stroke of the Z1-axis.
Numeral 64 denotes a third tool post, which is controlled only in the Z-axis direction along a Z3-axis. The movement of the Z3-axis is also superposed on that of the Z1-axis.
Control of a multitude of axes is effected by controlling the axes according to paths or channels. FIG. 4 shows the relationships between the channels and the axes to be controlled. As shown in FIG. 4, the X1-, Z1-, C-, and Z2-axes are controlled in a channel-1, the X2-, Z2-, C-, and Z1-axes are controlled in a channel-2, and the Z3- and X1-axes are controlled in a channel-3. The parenthesized alphabetical letters shown in FIG. 4 indicate program addresses in the channels.
One and the same axis is contained in a plurality of channels so that each axis is controlled in the individual channel, depending on the machining condition. For example, the C-axis is controlled in the channel-1 when the workpiece is machined by using the main spindle 61 and the first tool post 62, and is controlled in the channel-2 when the workpiece is machined by using the main spindle 61 and the second tool post 63.
In a conventional numerical control apparatus used for such a multiple-axis and multiple-channel machine tool, the operational capacity of processors is not sufficient for the processing of data input from a multitude of channels and the generation of servo commands for a multitude of axes. Namely, the machining speed is lowered, that is, a required machining speed cannot be obtained, and thus the advantages of the multiple-axis and multiple-channel machine tool cannot be fully realized.